How to bind a midi signal to tkinter?

[Gribouillis]

I don't see how running the render() function in a different thread makes it slower. Usually people don't want to run a time consuming function in the main thread because the GUI is frozen during the computation. The task of the mainloop() is to process events, not run heavy computations.

It seems to me there must be some other reason for the short blink on the screen, which won't be solved by running the function in the main thread.